1. The Field of the Invention
The present invention relates to a method of making a hydrolysis-resistant glass, the glass obtained with this method, and to articles made using this glass.
2. The Related Art
Glass with strong UV absorbing properties is known and is used especial-lly for manufacturing of gas discharge tubes and fluorescent lights and for making liquid crystal displays (LCD). Above all, a fluorescent light is used as a light source for a rear side illuminated display, i.e. the so-called backlight display.
Fluorescent lamp glass for the above-described usage, which absorbs UV radiation in the desired range, is known from U.S. Pat. No. 5,747,399. However it has been shown that this sort of glass is characterized by strong discoloration and in some cases strong solarization. Frequently a yellow brown discoloration arises when the raw material for the glass is melted.
A borosilicate glass containing zirconium oxide and lithium oxide of high strength, which is especially suited for use as a sealing glass with Fe—Co—Ni alloys, is known from DE-A 198 42 942. This sort of glass can contain color-imparting ingredients, such as Fe2O3, Cr2O3, CoO, and TiO2.
A solarization-stable borosilicate glass is known from DE-A 101 08 992, which is used for a so-called backlight for the background of displays in PCs, laptops, pocket calculators, etc, may be sealed in a vacuum-tight manner with tungsten. This sort of glass has a high content of SiO2 and B2O3, and a reduced amount of alkali oxides but with the sodium content clearly overweight.
DE 102 53 756 A1 describes a borosilicate glass with a high UV blocking action and its use as a fluorescent lamp. A glass of this sort has a high light permeability and a reduced UV transmission, but also a low processing temperature.
DE 10 2004 027 120 A1 describes a borosilicate glass with a high chemical resistance, which is manufactured with a raw material having a high iron content under oxidative conditions. This glass is also used for a fluorescent lamp, Xenon lamp, LCDs and displays, especially background lights.
Finally also DE 10 2004 027 119 A1 describes a UV radiation absorbing glass with small absorption in the visible range, which is substantially free of refining agents such as chloride, sulfate and/or antimony and which is refined under oxidative conditions with As2O3. This sort of glass contains TiO2 if necessary together with Fe2O3 for adjustment of the UV cutoff. Although all these glasses described above have outstanding properties for the uses described, it has been shown that they have no sufficient hydrolytic resistance under extreme conditions and especially they react with a fluorescent coating. This sort of reaction leads to a change in the color shade or color location of the light generated by a fluorescent light with a lamp bulb made from these glasses.